1. Field of the Invention
The present invention concerns a centrifuge comprising a rotational drive head attached to a rotation shaft, a rotor adapted to be removably mounted on the drive head in a rotational driving position, coupling means for coupling the drive head and the rotor in rotation, and a locking device for axially locking the rotor to the drive head comprising means for applying to the rotor an axial retaining force for retaining a bearing surface of the rotor against a retaining surface fastened to the drive head.
2. Description of the Related Art
Centrifuges of the above kind are used in particular in the biological field for centrifuging products contained in containers disposed in housings formed in the rotor.
A drive head of a centrifuge of the above kind generally has a vertical axis and extends the upper part of a drive shaft. A corresponding rotor is provided with an opening at the bottom to receive the head.
When the rotor is rotated by the drive head, the head is subjected to forces that tend to separate it axially from the drive head and to cause it to lift off.
Various devices for axially locking the rotor to the drive head exist already.
Document WO 83/04379 describes a centrifuge of the aforementioned type in which the axial retention force on the rotor is exerted by a coil spring bearing on a top shoulder on a lid closing the rotor and on a bottom shoulder on an actuator member a rod which is adapted to be retained axially by clipping into axial bore in the drive head.
A user can separate the rotor and the drive head manually using the actuator member and compressing the coil spring.
In the above centrifuge the axial retaining force is constant and limited to values enabling manual use of the actuator member.
The axial retaining force can prove insufficient, in particular at high rotation speeds, like those encountered in ultracentrifuges, which can be as high as 150 000 rpm.
What is more, the centrifuge described in document WO 83/04379 involves using a lid closing the rotor to assure the axial locking of the rotor to the drive head, which complicates the operations of mounting the rotor on the drive head and demounting it therefrom.